Phase Transition of Trapped Nuclear Exciton of Long-lived Rhodium Mossbauer States

We report experimental observations of the long-lived rhodium Mossbauer emissions by the time- and energy-resolved spectroscopy. The extraordinary observations manifest the open-up of photonic band gap in analogy to the superconducting gap of remarkable symmetry breakings at transition point. These observations are of potential importance for detecting gravitational waves and development of the two-photon gamma laser. Firstly, phase transitions shown by spectral evolution of characteristic emissions reveal the different aggregate exciton orderings at room temperature. Six different phases are identified by spectra profiles emitted from the color centers. Secondly, the cascade branching of the multipolar nuclear transition is discovered being the spontaneous cascade down-conversion to generate entangled gammas. The macroscopic angular distribution of entangled gammas from the polycrystalline sample manifests a global photon-nucleus-photon bound state across the grain boundaries. Thirdly, the gamma-energy distributions depending on exciton phases reveal the photonic band gap typically on the order of several hundred eV.